1. Field of the Invention
This invention generally relates to an apparatus for reproducing information from a recording medium. This invention specifically relates to an information reproducing apparatus including a waveform equalization circuit for processing a reproduced signal of a run-length-limited code.
2. Description of the Related Art
Japanese published unexamined patent application 10-106161 discloses an optical information reproducing apparatus based on a PRML (partial response maximum likelihood) system. In the apparatus of Japanese patent application 10-106161, information of a run-length-limited code is reproduced from an optical disc through a reproducing section, and a transversal filter subjects the reproduced waveform to partial-response equalization.
The output signal of the transversal filter is decoded into binary data by a maximum-likelihood decoder. The apparatus of Japanese patent application 10-106161 includes a parameter setting device which selects intersymbol-interference imparting values in the partial-response equalization in accordance with the characteristics of the reproduced waveform. Also, the parameter setting device sets tap coefficients of the transversal filter and a decision point signal level for the maximum-likelihood decoder as parameters in response to the selected intersymbol-interference imparting values.
The apparatus of Japanese patent application 10-106161 premises that the optical disc has predetermined pits (reference pits) representative of parameter-setting reference data.
Accordingly, the apparatus of Japanese patent application 10-106161 fails to implement suitable waveform equalization for an optical disc which lacks such predetermined pits.
Japanese published unexamined patent application 7-192270 discloses an apparatus for reproducing a digital signal of a run-length-limited code from an optical disc. The apparatus of Japanese patent application 7-192270 uses a method suited for a high information recording density. The method in Japanese patent application 7-192270 performs ternary equalization whose objects are only an amplitude except for points corresponding to a data train provided with a minimum code inverting gap among points just before or just after the inverting position of a code and an amplitude at the inverting position of the code.
In the apparatus of Japanese patent application 7-192270, a signal is read from an optical disc by an optical head, and the read signal is applied through an amplifier to an equalizer. A decider following the equalizer discriminates the level of the output signal of the equalizer. The decider includes two comparators. The output signals of the comparators are fed to an error calculation circuit as level discrimination results. Since the decider includes the two comparators, the signal processing by the decider and also an error calculation process are relatively complicated.
It is an object of this invention to provide an improved reproducing apparatus.
A first aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; a transversal filter subjecting the signal reproduced by the first means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; second means for detecting whether or not the signal reproduced by the first means corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the second means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; third means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; and fourth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the third means.
A second aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus wherein at least one of the PR mode signal and the RLL mode signal remains fixed.
A third aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus further comprising fifth means for subjecting the signal reproduced by the first means to a re-sampling process to generate a re-sampling resultant signal, and feeding the re-sampling resultant signal to the transversal filter.
A fourth aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; a transversal filter subjecting the signal reproduced by the first means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; second means for detecting whether or not the equalization-resultant signal generated by the transversal filter corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the second means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; third means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; and fourth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the third means.
A fifth aspect of this invention is based on the fourth aspect thereof, and provides a reproducing apparatus wherein the second means comprises means for detecting a polarity inversion of the equalization-resultant signal, means for selecting one of two samples of the equalization-resultant signal which are adjacent to the detected polarity inversion, the selected one of the samples being closer to a value of xe2x80x9c0xe2x80x9d, and means for generating the 0-point information in response to the selected sample.
A sixth aspect of this invention is based on the fourth aspect thereof, and provides a reproducing apparatus further comprising fifth means for generating a signal representing a phase error between a bit clock signal and the zero-cross point of the equalization-resultant signal.
A seventh aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus wherein the type of the partial-response waveform equalization which is represented by the PR mode signal is expressed as PR (a, b, b, a), and the successive samples of the 0-point information are three successive samples, and wherein the temporary decision device comprises means for calculating a value P on the basis of the successive samples of the 0-point information, the value P being equal to (a+b)*xc2x7G when none of the successive samples of the 0-point information corresponds to a zero-cross point, the value P being equal to (bxe2x88x92a)*xc2x7G when each of the successive samples of the 0-point information except a central sample corresponds to a zero-cross point and a minimum transition interval represented by the RLL mode signal is equal to xe2x80x9c2xe2x80x9d, the value P being equal to b*xc2x7G when each of the successive samples of the 0-point information except a central sample corresponds to a zero-cross point and the minimum transition interval represented by the RLL mode signal is not equal to xe2x80x9c2xe2x80x9d, the value P being equal to b*xc2x7G when only one of the successive samples of the 0-point information except a central sample corresponds to a zero-cross point, means for calculating the temporary decision value on the basis of the calculated value P, and means for setting the temporary decision value equal to xe2x80x9c0xe2x80x9d when the central sample among the successive samples of the 0-point information corresponds to a zero-cross point, where xe2x80x9c*xe2x80x9d denotes related values resulting from offset to equalize a central value (a+b) to xe2x80x9c0xe2x80x9d, and G denotes a gain factor.
An eighth aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus wherein the type of the partial-response waveform equalization which is represented by the PR mode signal is expressed as PR (a, b, b, a), and the successive samples of the 0-point information are five successive samples, and wherein the temporary decision device comprises means for calculating a value P on the basis of the successive samples of the 0-point information, the value P being equal to (a+b)*xc2x7G when none of second, third, and fourth samples among the successive samples of the 0-point information corresponds to a zero-cross point, the value P being equal to (bxe2x88x92a)*xc2x7G when only second and fourth samples among the successive samples of the 0-point information correspond to zero-cross points and a minimum transition interval represented by the RLL mode signal is equal to xe2x80x9c2xe2x80x9d, the value P being equal to b*xc2x7G when only second and fourth samples among the successive samples of the 0-point information correspond to zero-cross points and the minimum transition interval represented by the RLL mode signal is not equal to xe2x80x9c2xe2x80x9d, the value P being equal to b*xc2x7G when only one of second and fourth samples among the successive samples of the 0-point information corresponds to a zero-cross point, the value P being equal to b*xc2x7G when only first and fourth samples among the successive samples of the 0-point information corresponds to a zero-cross point, the value P being equal to b*xc2x7G when only second and fifth samples among the successive samples of the 0-point information corresponds to a zero-cross point, means for calculating the temporary decision value on the basis of the calculated value P, and means for setting the temporary decision value equal to xe2x80x9c0xe2x80x9d when a central sample among the successive samples of the 0-point information corresponds to a zero-cross point, where xe2x80x9c*xe2x80x9d denotes related values resulting from offset to equalize a central value (a+b) to xe2x80x9c0xe2x80x9d, and G denotes a gain factor.
A ninth aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus further comprising an error selection circuit for extracting effective components from the first error signal in response to the temporary decision value, and generating a second error signal in response to the extracted effective components.
A tenth aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus further comprising an error selection circuit for extracting effective components from the first error signal in response to the successive samples of the 0-point information, and generating a second error signal in response to the extracted effective components.
An eleventh aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus wherein the type of the partial-response waveform equalization which is represented by the PR mode signal is expressed as PR (a, b, b, a), and the successive samples of the 0-point information are three successive samples, and wherein the temporary decision device comprises means for calculating a value P on the basis of the successive samples of the 0-point information, the value P being equal to (bxe2x88x92a)*xc2x7G when each of the successive samples of the 0-point information except a central sample corresponds to a zero-cross point and a minimum transition interval represented by the RLL mode signal is equal to xe2x80x9c2xe2x80x9d, the value P being equal to b*xc2x7G when each of the successive samples of the 0-point information except a central sample corresponds to a zero-cross point and the minimum transition interval represented by the RLL mode signal is not equal to xe2x80x9c2xe2x80x9d, the value P being equal to b*xc2x7G when only one of the successive samples of the 0-point information except a central sample corresponds to a zero-cross point, means for calculating the temporary decision value on the basis of the calculated value P, means for setting the temporary decision value equal to xe2x80x9c0xe2x80x9d when none of the successive samples of the 0-point information corresponds to a zero-cross point, and means for setting the temporary decision value equal to xe2x80x9c0xe2x80x9d when the central sample among the successive samples of the 0-point information corresponds to a zero-cross point, where xe2x80x9c*xe2x80x9d denotes related values resulting from offset to equalize a central value (a+b) to xe2x80x9c0xe2x80x9d, and G denotes a gain factor.
A twelfth aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus wherein the type of the partial-response waveform equalization which is represented by the PR mode signal is expressed as PR (a, b, b, a), and the successive samples of the 0-point information are five successive samples, and wherein the temporary decision device comprises means for calculating a value P on the basis of the successive samples of the 0-point information, the value P being equal to (bxe2x88x92a)*xc2x7G when only second and fourth samples among the successive samples of the 0-point information correspond to zero-cross points and a minimum transition interval represented by the RLL mode signal is equal to xe2x80x9c2xe2x80x9d, the value P being equal to b*xc2x7G when only second and fourth samples among the successive samples of the 0-point information correspond to zero-cross points and the minimum transition interval represented by the RLL mode signal is not equal to xe2x80x9c2xe2x80x9d, the value P being equal to b*xc2x7G when only one of second and fourth samples among the successive samples of the 0-point information corresponds to a zero-cross point, the value P being equal to b*xc2x7G when only first and fourth samples among the successive samples of the 0-point information corresponds to a zero-cross point, the value P being equal to b*xc2x7G when only second and fifth samples among the successive samples of the 0-point information corresponds to a zero-cross point, means for calculating the temporary decision value on the basis of the calculated value P, means for setting the temporary decision value equal to xe2x80x9c0xe2x80x9d when none of second, third, and fourth samples among the successive samples of the 0-point information corresponds to a zero-cross point, and means for setting the temporary decision value equal to xe2x80x9c0xe2x80x9d when a central sample among the successive samples of the 0-point information corresponds to a zero-cross point, where xe2x80x9c*xe2x80x9d denotes related values resulting from offset to equalize a central value (a+b) to xe2x80x9c0xe2x80x9d, and G denotes a gain factor.
A thirteenth aspect of this invention is based on the first aspect thereof, and provides a reproducing apparatus further comprising a first memory into which the signal reproduced by the first means is written in response to a bit clock signal, and from which the reproduced signal is read out in response to a new clock signal before being fed to the transversal filter, and a second memory into which the 0-point information generated by the second means is written in response to the bit clock signal, and from which the 0-point information is read out in response to a new clock signal before being fed to the delay circuit.
A fourteenth aspect of this invention is based on the fourth aspect thereof, and provides a reproducing apparatus further comprising a memory into which the signal reproduced by the first means is written in response to a bit clock signal, and from which the reproduced signal is read out in response to a new clock signal before being fed to the transversal filter.
A fifteenth aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; a subtracter for subtracting a DC offset signal from the signal reproduced by the first means to generate a subtraction-resultant signal; second means for subjecting the subtraction-resultant signal generated by the subtracter to a re-sampling process to generate a re-sampling resultant signal; third means for detecting whether or not the re-sampling resultant signal generated by the second means corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; and an error calculator for selecting some signals from the re-sampling resultant signal in response to the 0-point information generated by the third means, and extracting 0-corresponding components and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
A sixteenth aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; second means for subjecting the signal reproduced by the first means to a re-sampling process to generate a re-sampling resultant signal; a subtracter for subtracting a DC offset signal from the re-sampling resultant signal generated by the second means to generate a subtraction-resultant signal; a transversal filter subjecting the subtraction-result signal generated by the subtracter to a partial-response waveform equalization to generate an equalization-resultant signal; third means for detecting whether or not the re-sampling resultant signal generated by the second means corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; and an error calculator for selecting 0-corresponding components from the re-sampling resultant signal in response to the 0-point information generated by the third means, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
A seventeenth aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; a subtracter for subtracting a DC offset signal from the signal reproduced by the first means to generate a subtraction-resultant signal; second means for subjecting the subtraction-resultant signal generated by the subtracter to a re-sampling process to generate a re-sampling resultant signal; a transversal filter subjecting the re-sampling resultant signal generated by the second means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; third means for detecting whether or not the re-sampling resultant signal corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the third means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; fourth means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; fifth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the fourth means; and an error calculator for selecting 0-corresponding components from the error signal in response to one of the successive samples of the 0-point information, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
An eighteenth aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; second means for subjecting the signal reproduced by the first means to a re-sampling process to generate a re-sampling resultant signal; a transversal filter subjecting the re-sampling resultant signal generated by the second means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; a subtracter for subtracting a DC offset signal from the equalization-resultant signal generated by the transversal filter to generate a subtraction-resultant signal; third means for detecting whether or not the re-sampling resultant signal corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the third means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; fourth means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; fifth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the fourth means; and an error calculator for selecting 0-corresponding components from the error signal in response to one of the successive samples of the 0-point information, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
A nineteenth aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; a subtracter for subtracting a DC offset signal from the signal reproduced by the first means to generate a subtraction-resultant signal; second means for subjecting the subtraction-resultant signal generated by the subtracter to a re-sampling process to generate a re-sampling resultant signal; a transversal filter subjecting the re-sampling resultant signal generated by the second means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; third means for detecting whether or not the re-sampling resultant signal corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the third means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; fourth means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; fifth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the fourth means; and an error calculator for selecting 0-corresponding components from the error signal in response to the temporary decision value, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
A twentieth aspect of this invention provides a reproducing a apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; second means for subjecting the signal reproduced by the first means to a re-sampling process to generate a re-sampling resultant signal; a transversal filter subjecting the re-sampling resultant signal generated by the second means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; a subtracter for subtracting a DC offset signal from the equalization-resultant signal generated by the transversal filter to generate a subtraction-resultant signal; third means for detecting whether or not the re-sampling resultant signal corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the third means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; fourth means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; fifth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the fourth means; and an error calculator for selecting 0-corresponding components from the error signal in response to the temporary decision value, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
A twenty-first aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; a subtracter for subtracting a DC offset signal from the signal reproduced by the first means to generate a subtraction-resultant signal; second means for subjecting the subtraction-resultant signal generated by the subtracter to a re-sampling process to generate a re-sampling resultant signal; a transversal filter subjecting the re-sampling resultant signal generated by the second means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; third means for detecting whether or not the re-sampling resultant signal corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the third means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; fourth means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; fifth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the fourth means; and an error calculator for selecting 0-corresponding components from the equalization-resultant signal in response to at least one of the successive samples of the 0-point information, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
A twenty-second aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; second means for subjecting the signal reproduced by the first means to a re-sampling process to generate a re-sampling resultant signal; a transversal filter subjecting the re-sampling resultant signal generated by the second means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; a subtracter for subtracting a DC offset signal from the equalization-resultant signal generated by the transversal filter to generate a subtraction-resultant signal; third means for detecting whether or not the re-sampling resultant signal corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the third means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; fourth means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; fifth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the fourth means; and an error calculator for selecting 0-corresponding components from the equalization-resultant signal in response to one of the successive samples of the 0-point information, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
A twenty-third aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; a subtracter for subtracting a DC offset signal from the signal reproduced by the first means to generate a subtraction-resultant signal; second means for subjecting the subtraction-resultant signal generated by the subtracter to a re-sampling process to generate a re-sampling resultant signal; a transversal filter subjecting the re-sampling resultant signal generated by the second means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; third means for detecting whether or not the re-sampling resultant signal corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the third means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; fourth means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; fifth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the fourth means; and an error calculator for selecting 0-corresponding components from the equalization-resultant signal in response to the temporary decision value, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.
A twenty-fourth aspect of this invention provides a reproducing apparatus comprising first means for reproducing a signal of a run-length-limited code from a recording medium; second means for subjecting the signal reproduced by the first means to a re-sampling process to generate a re-sampling resultant signal; a transversal filter subjecting the re-sampling resultant signal generated by the second means to a partial-response waveform equalization to generate an equalization-resultant signal, the partial-response waveform equalization depending on tap coefficients; a subtracter for subtracting a DC offset signal from the equalization-resultant signal generated by the transversal filter to generate a subtraction-resultant signal; third means for detecting whether or not the re-sampling resultant signal corresponds to a zero-cross point, and generating 0-point information in response to a result of said detecting; a delay circuit responsive to the 0-point information generated by the third means for outputting at least three successive samples of the 0-point information; a temporary decision device for calculating a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, the successive samples of the 0-point information which are outputted from the delay circuit, and an actual value of the equalization-resultant signal, the PR mode signal representing a type of the partial-response waveform equalization, the RLL mode signal representing a type of the run-length-limited code; fourth means for calculating a difference between the temporary decision value of the equalization-resultant signal and the actual value thereof, and generating an error signal in response to the calculated difference; fifth means for controlling the tap coefficients of the transversal filter in response to the error signal generated by the fourth means; and an error calculator for selecting 0-corresponding components from the equalization-resultant signal in response to the temporary decision value, and generating the DC offset signal in response to the selected 0-corresponding components and outputting the DC offset signal to the subtracter.